Unloading device for pumps.



E. H. DEWSON.

UNLOADING DEVICE FOR PUMPS. APPiIOA'IIOH FILED SEPT. 3, 1907.

WITWEQB'ES INVENTOR Patented; May 6, 1913.

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EDWARD H. DEWSON, OF NEW YORK, N. Y., ASSIGNOR TO THE WESTINGHOUSE BRAKE COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA.

Specification of Letters Patent.

Patented May 6, 1913.

Application filed September 3, 1807. Serial No. 391,120.

To all whom it may concern:

Be it known that I, EDWARD H. Dawson, a citizen of theUnited States, residing at New Yorit, in the county of New York and State of New York, have invented new and useful Improvements in Unloading Devices for Pumps, of which the following is a specification.

the system,

the opening and the closing of an electric switch in the motor-},circuit, whereby the pump is periodically o erated to maintain a certain predetermined fluid pressure in the system. The pump at starting, is of course subject to the pressure in the system, and consequently the motor starts under a considerableload, thereby consuming a correspondingly heavy current, which sometimes causes damage to the motor. Also, in the case of induction motors, having a low starting torque, it may be difficult for the motor to speed up under the starting load of the pump. It has been proposed to obviate this ditficulty, bycompressing the fluid into a primary reservoir or receptacle, connected to the usual storage reservoir and system through a non-return check valve, and providing meansfor releasing the fluid from the primary reservoir when the motor is cut out and the pump stops, so that when the motor is started,- the pump' operates under a light load, until the pressure in the primary reservoir is again pumpedup. The means above referred to comprises a magnet in the p ump motor circuit, and a release valve, controlled by the magnet, to vent fluid from the primary chamber upon the opening of the motor circuit and the stopping of the pump.

, It is; the principal object of my invention to provide an improved unloading device of the above character, wherein the pump governor controls the reductionin pressure of the fluid acting against the pump piston.

In the accompanying drawing, Figure 1 is a diagrammatic'view, illustrating a general application of one form of my invention to a motor air compressor equipment, and Fig. 2 a similar view, more in detail, of another form of my improvements, as ap plied in connection with a particular design of pump governor.

The apparatus illustrated in Fig. 1 of the drawing, comprises an electric motor driven air compressor 1, a storage reservoir 2, and an electric pump governor 3, connected to the storage reservoir 2 by a pipe 4:, all of which may be of the usual construction. According to my improvements, the

outlet pipe 5 of the motor compressor 1 is connected, preferably, to an enlarged receptacle or reservoir 6, which opens through a pipe 7, containin a non-return check valve 8, into the main storage reservoir 2. The small reservoir 6, which may be termed the primary reservoir, is connected by a pipe 10 to a casing containing a vent valve 9, normally seated by a spring 11, and governing an atmospheric port 14. The vent valve 9 is provided with a projecting stem 12, and the casing is mounted on the governor 3, so that the stem 12 may be engaged, and the vent valve opened, by the move' ment of some part of the governor to the cut out position. As shown in the drawing, this moving part may be the stem 13 of the actuating piston for the electric switch controlling the motor circuit. At starting,'the

motor being cut in, the pump compresses fluid into the primary reservoir 6 and thence, through the check valve 8 and pipe 7, t0 the storage reservoir 2, and when the pressure therein has attained the degree at which the governor is adjusted, the switch opens and the pump stops as usual. The movement of the piston stem outwardly, opens the ve'nt valve 9, and releases fluid from the pipe 10 and the primary reservoir 6, further venting of fluid beyond said reservoirbeing prevented by the check valve 8. When the fluid pressure of the system has been reduced to the point at which the governor acts to close the electric switch, the vent valve is permitted to close, and it will be apparent, that since the fluidpressure is reduced on the pump piston, the inotor starts under a considerably reduced load, and so the motor speed readily develops,

without material hindrance. It will also be apparent that the venting of fluid from the pump piston by the action of the pump piston heads, 17 and 18, which are adapted to permit leakage of fluid from .the 'intermediate valve chamber, open to fluid at pump pressure, to the respective outer chambers of the piston heads 17 and-'18. A high tension regulating mechanism, comprising a diaphragm 19, subject to pump pressure, controls a release valve 20, for venting fluid from one of the piston heads 17, so that the fluid pressure on the opposite piston head 18 shifts the abutment and main valve 15 and admits fluid under pressure to said actuating piston, to cause theswitch 16'to open and cut out the motor and pump, and .a low tension regulating mechanism, comprising a diaphragm 21, subject to pump pressure, and adapted, upon a predetermined reduction in pump pressure, to actuate a release valve 22, to vent fluid from the piston head 18, so that the pressure on the opposite'head 1f? shifts the'abutment and main valve 15 to release fluid from the actuating piston f of the switch 16, thereby closing the switch and causing the pump to cut in. In this type of governor, the high tension diaphragm is connected, in the cut out posit ion,

y the main valve 15, with an exhaust port 23, through passage 24, leading to the diaphragm, in order to permit the release valve 20 to close and thereby prevent leakage therethrough. According to my invention the pipe 10 from the primary reservoir 6 may be connected to the chamber of the diaphragm 19, with the result that the reservoir 6 is open to the exhaust port 23 in the cut out osition of the parts, and fluid is vented fli'om the primary reservoir, thus utilizing the governor mechanism, to accomplish the desired result, by merely tapping the pipe 10 into the chamber of the diaphragm -19.

It may not benecessary to relieve the pump of its full starting load in some instances, and for the sake of economy of air, a certain amount of fluid may be retained in the primary reservoir. For this purpose, an adjustable load valve 25, may be interposed in' the pipe 10, the load spring 26, of which, is adjusted to retain a certain amount of fluid, as may be considered desirab1e,'so that when fluid is released from the primary reservoir 6, the load,, valve 25 closes, when the pressure is reduced to the desired degree. The casing 27, containing the load valve 25,

It will now be apparent that I have provided an extremely simple means for relieving the pump of its load at starting, which may be readily applied to various types of pressure governors for pumps, without interfering with the normal and usual operation of the governor, and that with my improvements any predetermined desired reduction in the pressure acting against the pump piston at starting'may be obtained.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is 1. In a pressure control apparatus, the combination with a pump and a pump governor, of a receptacle into which said pum-p compresses fluid, and means operated by a moving part of said governor, for releasing fluid from said receptacle.

2. In a pressure control apparatus, the combination with a pump and a pump governor, of a receptacle into which said pump compresses fluid, and valve means, operated by a moving part of said governor in the movement to cut out position, for releasing fluid from said receptacle.

3. In a pressure control apparatus, the combination with a pump, a reservoir, and a governor, subject to reservoir pressure, for controlling said pump, of a receptacle intermediate said reservoir and pump, into which said pump compresses fluid, a check valve for preventing back flow from the reservoir to said receptacle, and means, operated by a moving part of said governor in the movement to cut out position, for releasing fluid from said receptacle. I

4'. In a pressure control apparatus, the combination, with a pump, of a governor for said pump comprising a controlling device,

starting, and meansfor limiting said reduction in pressure.

6. In a pressure control apparatus, the

combination with a pump and a pump governor, of a release valve operated by a moving part of said governor for reducing the pressure acting on the pump piston at starting, and a load valve means for limiting the reduction in pressure to a predetermined de ree.

. I. In a pressure control apparatus, the combination with a pump, of a overnor for said pump comprising a centre ling device,

an actuating piston therefor, a main valve and abutment for controlling the fluid pressure on said piston, a regulating valve mechanism for controlling the act-ion of said abutment and main valve, and means controlled by said main valve for releasing fluid from said regulating valve mechanism and from the ump plston, upon movement thereof to t e cut out position.

8. In a pressure control apparatus, the combination with a pump, of a governor for said pump comprising a controlling device and a valve mechanism governed by the pump pressure for operating the controlling device, said valve mechanism being adapted to relieve the pump piston of pressure upon movement to out out the pump.

9. Ina pressure control apparatus, the combinatlon with a fluid compressor, of a governor for said compressor comprising a controlling device, a valve for controlling I the fluid pressure for operatingsaid controlling device, a-movable abutmentfor actuating said valve, and a regulating valve my hand.

EDWARD H. DEWSON.

Witnesses:

ALFRED K. GAVEY, W. L. SNIDER. 

